unittests/StaticAnalyzer/BlockEntranceCallbackTest.cpp - llvm-project/clang - Git at Google

 //===- unittests/StaticAnalyzer/BlockEntranceCallbackTest.cpp -------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//

 #include "CheckerRegistration.h"
 #include "clang/Analysis/AnalysisDeclContext.h"
 #include "clang/Analysis/ProgramPoint.h"
 #include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
 #include "clang/StaticAnalyzer/Core/Checker.h"
 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState_Fwd.h"
 #include "clang/StaticAnalyzer/Frontend/AnalysisConsumer.h"
 #include "clang/StaticAnalyzer/Frontend/CheckerRegistry.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/raw_ostream.h"
 #include "gtest/gtest.h"

 using namespace clang;
 using namespace ento;

 namespace {

 class BlockEntranceCallbackTester final : public Checker<check::BlockEntrance> {
   const BugType Bug{this, "BlockEntranceTester"};

 public:
   void checkBlockEntrance(const BlockEntrance &Entrance,
                           CheckerContext &C) const {
     ExplodedNode *Node = C.generateNonFatalErrorNode(C.getState());
     if (!Node)
       return;

     const auto *FD =
         cast<FunctionDecl>(C.getLocationContext()->getStackFrame()->getDecl());

     std::string Description = llvm::formatv(
         "Within '{0}' B{1} -> B{2}", FD->getIdentifier()->getName(),
         Entrance.getPreviousBlock()->getBlockID(),
         Entrance.getBlock()->getBlockID());
     auto Report =
         std::make_unique<PathSensitiveBugReport>(Bug, Description, Node);
     C.emitReport(std::move(Report));
   }
 };

 class BranchConditionCallbackTester final
     : public Checker<check::BranchCondition> {
   const BugType Bug{this, "BranchConditionCallbackTester"};

 public:
   void checkBranchCondition(const Stmt *Condition, CheckerContext &C) const {
     ExplodedNode *Node = C.generateNonFatalErrorNode(C.getState());
     if (!Node)
       return;
     const auto *FD =
         cast<FunctionDecl>(C.getLocationContext()->getStackFrame()->getDecl());

     std::string Buffer =
         (llvm::Twine("Within '") + FD->getIdentifier()->getName() +
          "': branch condition '")
             .str();
     llvm::raw_string_ostream OS(Buffer);
     Condition->printPretty(OS, /*Helper=*/nullptr,
                            C.getASTContext().getPrintingPolicy());
     OS << "'";
     auto Report = std::make_unique<PathSensitiveBugReport>(Bug, Buffer, Node);
     C.emitReport(std::move(Report));

     C.addTransition();
   }
 };

 template <typename Checker> void registerChecker(CheckerManager &Mgr) {
   Mgr.registerChecker<Checker>();
 }

 bool shouldAlwaysRegister(const CheckerManager &) { return true; }

 void addBlockEntranceTester(AnalysisASTConsumer &AnalysisConsumer,
                             AnalyzerOptions &AnOpts) {
   AnOpts.CheckersAndPackages.emplace_back("test.BlockEntranceTester", true);
   AnalysisConsumer.AddCheckerRegistrationFn([](CheckerRegistry &Registry) {
     Registry.addChecker(&registerChecker<BlockEntranceCallbackTester>,
                         &shouldAlwaysRegister, "test.BlockEntranceTester",
                         "EmptyDescription", "EmptyDocsUri",
                         /*IsHidden=*/false);
   });
 }

 void addBranchConditionTester(AnalysisASTConsumer &AnalysisConsumer,
                               AnalyzerOptions &AnOpts) {
   AnOpts.CheckersAndPackages.emplace_back("test.BranchConditionTester", true);
   AnalysisConsumer.AddCheckerRegistrationFn([](CheckerRegistry &Registry) {
     Registry.addChecker(&registerChecker<BranchConditionCallbackTester>,
                         &shouldAlwaysRegister, "test.BranchConditionTester",
                         "EmptyDescription", "EmptyDocsUri",
                         /*IsHidden=*/false);
   });
 }

 llvm::SmallVector<StringRef> parseEachDiag(StringRef Diags) {
   llvm::SmallVector<StringRef> Fragments;
   llvm::SplitString(Diags, Fragments, "\n");
   // Drop the prefix like "test.BlockEntranceTester: " from each fragment.
   for (StringRef &Fragment : Fragments) {
     Fragment = Fragment.drop_until([](char Ch) { return Ch == ' '; });
     Fragment.consume_front(" ");
   }
   llvm::sort(Fragments);
   return Fragments;
 }

 template <AddCheckerFn Fn = addBlockEntranceTester, AddCheckerFn... Fns>
 bool runChecker(const std::string &Code, std::string &Diags) {
   std::string RawDiags;
   bool Res = runCheckerOnCode<Fn, Fns...>(Code, RawDiags,
                                           /*OnlyEmitWarnings=*/true);
   llvm::raw_string_ostream OS(Diags);
   llvm::interleave(parseEachDiag(RawDiags), OS, "\n");
   return Res;
 }

 [[maybe_unused]] void dumpCFGAndEgraph(AnalysisASTConsumer &AnalysisConsumer,
                                        AnalyzerOptions &AnOpts) {
   AnOpts.CheckersAndPackages.emplace_back("debug.DumpCFG", true);
   AnOpts.CheckersAndPackages.emplace_back("debug.ViewExplodedGraph", true);
 }

 /// Use this instead of \c runChecker to enable the debugging a test case.
 template <AddCheckerFn... Fns>
 [[maybe_unused]] bool debugChecker(const std::string &Code,
                                    std::string &Diags) {
   return runChecker<dumpCFGAndEgraph, Fns...>(Code, Diags);
 }

 std::string expected(SmallVector<StringRef> Diags) {
   llvm::sort(Diags);
   std::string Result;
   llvm::raw_string_ostream OS(Result);
   llvm::interleave(Diags, OS, "\n");
   return Result;
 }

 TEST(BlockEntranceTester, FromEntryToExit) {
   constexpr auto Code = R"cpp(
   void top() {
     // empty
   })cpp";

   std::string Diags;
   // Use "debugChecker" instead of "runChecker" for debugging.
   EXPECT_TRUE(runChecker(Code, Diags));
   EXPECT_EQ(expected({"Within 'top' B1 -> B0"}), Diags);
 }

 TEST(BlockEntranceTester, SingleOpaqueIfCondition) {
   constexpr auto Code = R"cpp(
   bool coin();
   int glob;
   void top() {
     if (coin()) {
       glob = 1;
     } else {
       glob = 2;
     }
     glob = 3;
   })cpp";

   std::string Diags;
   // Use "debugChecker" instead of "runChecker" for debugging.
   EXPECT_TRUE(runChecker(Code, Diags));
   EXPECT_EQ(expected({
                 "Within 'top' B1 -> B0",
                 "Within 'top' B2 -> B1",
                 "Within 'top' B3 -> B1",
                 "Within 'top' B4 -> B2",
                 "Within 'top' B4 -> B3",
                 "Within 'top' B5 -> B4",
             }),
             Diags);
   // entry true                   exit
   //  B5 -------> B4 --> B2 --> B1 --> B0
   //  |                         ^
   //  | false                   |
   //  v                         |
   //  B3 -----------------------+
 }

 TEST(BlockEntranceTester, TrivialIfCondition) {
   constexpr auto Code = R"cpp(
   bool coin();
   int glob;
   void top() {
     int cond = true;
     if (cond) {
       glob = 1;
     } else {
       glob = 2;
     }
     glob = 3;
   })cpp";

   std::string Diags;
   // Use "debugChecker" instead of "runChecker" for debugging.
   EXPECT_TRUE(runChecker(Code, Diags));
   EXPECT_EQ(expected({
                 "Within 'top' B1 -> B0",
                 "Within 'top' B3 -> B1",
                 "Within 'top' B4 -> B3",
                 "Within 'top' B5 -> B4",
             }),
             Diags);
   // entry  true                         exit
   // B5 ----------> B4 --> B3 --> B1 --> B0
 }

 TEST(BlockEntranceTester, AcrossFunctions) {
   constexpr auto Code = R"cpp(
   bool coin();
   int glob;
   void nested() { glob = 1; }
   void top() {
     glob = 0;
     nested();
     glob = 2;
   })cpp";

   std::string Diags;
   // Use "debugChecker" instead of "runChecker" for debugging.
   EXPECT_TRUE(runChecker(Code, Diags));
   EXPECT_EQ(
       expected({
           // Going from the "top" entry artificial node to the "top" body.
           // Ideally, we shouldn't observe this edge because it's artificial.
           "Within 'top' B2 -> B1",

           // We encounter the call to "nested()" in the "top" body, thus we have
           // a "CallEnter" node, but importantly, we also elide the transition
           // to the "entry" node of "nested()".
           // We only see the edge from the "nested()" entry to the "nested()"
           // body:
           "Within 'nested' B2 -> B1",

           // Once we return from "nested()", we transition to the "exit" node of
           // "nested()":
           "Within 'nested' B1 -> B0",

           // We will eventually return to the "top" body, thus we transition to
           // its "exit" node:
           "Within 'top' B1 -> B0",
       }),
       Diags);
 }

 TEST(BlockEntranceTester, ShortCircuitingLogicalOperator) {
   constexpr auto Code = R"cpp(
   bool coin();
   void top(int x) {
     int v = 0;
     if (coin() && (v = x)) {
       v = 2;
     }
     v = 3;
   })cpp";
   //                        coin(): false
   //              +--------------------------------+
   // entry        |                                v         exit
   // +----+     +----+     +----+     +----+     +----+     +----+
   // | B5 | --> | B4 | --> | B3 | --> | B2 | --> | B1 | --> | B0 |
   // +----+     +----+     +----+     +----+     +----+     +----+
   //                         |                     ^
   //                         +---------------------+
   //                            (v = x): false

   std::string Diags;
   // Use "debugChecker" instead of "runChecker" for debugging.
   EXPECT_TRUE(runChecker(Code, Diags));
   EXPECT_EQ(expected({
                 "Within 'top' B1 -> B0",
                 "Within 'top' B2 -> B1",
                 "Within 'top' B3 -> B1",
                 "Within 'top' B3 -> B2",
                 "Within 'top' B4 -> B1",
                 "Within 'top' B4 -> B3",
                 "Within 'top' B5 -> B4",
             }),
             Diags);
 }

 TEST(BlockEntranceTester, Switch) {
   constexpr auto Code = R"cpp(
   bool coin();
   int top(int x) {
     int v = 0;
     switch (x) {
       case 1:  v = 10; break;
       case 2:  v = 20; break;
       default: v = 30; break;
     }
     return v;
   })cpp";
   //            +----+
   //            | B5 | -------------------------+
   //            +----+                          |
   //              ^ [case 1]                    |
   // entry        |                             v         exit
   // +----+     +----+  [default]  +----+     +----+     +----+
   // | B6 | --> | B2 | ----------> | B3 | --> | B1 | --> | B0 |
   // +----+     +----+             +----+     +----+     +----+
   //              |                             ^
   //              v [case 2]                    |
   //            +----+                          |
   //            | B4 | -------------------------+
   //            +----+

   std::string Diags;
   // Use "debugChecker" instead of "runChecker" for debugging.
   EXPECT_TRUE(runChecker(Code, Diags));
   EXPECT_EQ(expected({
                 "Within 'top' B1 -> B0",
                 "Within 'top' B2 -> B3",
                 "Within 'top' B2 -> B4",
                 "Within 'top' B2 -> B5",
                 "Within 'top' B3 -> B1",
                 "Within 'top' B4 -> B1",
                 "Within 'top' B5 -> B1",
                 "Within 'top' B6 -> B2",
             }),
             Diags);
 }

 TEST(BlockEntranceTester, BlockEntranceVSBranchCondition) {
   constexpr auto Code = R"cpp(
   bool coin();
   int top(int x) {
     int v = 0;
     switch (x) {
       default: v = 30; break;
     }
     if (x == 6) {
       v = 40;
     }
     return v;
   })cpp";
   std::string Diags;
   // Use "debugChecker" instead of "runChecker" for debugging.
   EXPECT_TRUE((runChecker<addBlockEntranceTester, addBranchConditionTester>(
       Code, Diags)));
   EXPECT_EQ(expected({
                 "Within 'top' B1 -> B0",
                 "Within 'top' B2 -> B1",
                 "Within 'top' B3 -> B1",
                 "Within 'top' B3 -> B2",
                 "Within 'top' B4 -> B5",
                 "Within 'top' B5 -> B3",
                 "Within 'top' B6 -> B4",
                 "Within 'top': branch condition 'x == 6'",
             }),
             Diags);
 }

 } // namespace
	//===- unittests/StaticAnalyzer/BlockEntranceCallbackTest.cpp -------------===//
	//
	// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
	// See https://llvm.org/LICENSE.txt for license information.
	// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
	//
	//===----------------------------------------------------------------------===//

	#include "CheckerRegistration.h"
	#include "clang/Analysis/AnalysisDeclContext.h"
	#include "clang/Analysis/ProgramPoint.h"
	#include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
	#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
	#include "clang/StaticAnalyzer/Core/Checker.h"
	#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
	#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState_Fwd.h"
	#include "clang/StaticAnalyzer/Frontend/AnalysisConsumer.h"
	#include "clang/StaticAnalyzer/Frontend/CheckerRegistry.h"
	#include "llvm/ADT/STLExtras.h"
	#include "llvm/ADT/StringExtras.h"
	#include "llvm/ADT/StringRef.h"
	#include "llvm/ADT/Twine.h"
	#include "llvm/Support/FormatVariadic.h"
	#include "llvm/Support/raw_ostream.h"
	#include "gtest/gtest.h"

	using namespace clang;
	using namespace ento;

	namespace {

	class BlockEntranceCallbackTester final : public Checker<check::BlockEntrance> {
	const BugType Bug{this, "BlockEntranceTester"};

	public:
	void checkBlockEntrance(const BlockEntrance &Entrance,
	CheckerContext &C) const {
	ExplodedNode *Node = C.generateNonFatalErrorNode(C.getState());
	if (!Node)
	return;

	const auto *FD =
	cast<FunctionDecl>(C.getLocationContext()->getStackFrame()->getDecl());

	std::string Description = llvm::formatv(
	"Within '{0}' B{1} -> B{2}", FD->getIdentifier()->getName(),
	Entrance.getPreviousBlock()->getBlockID(),
	Entrance.getBlock()->getBlockID());
	auto Report =
	std::make_unique<PathSensitiveBugReport>(Bug, Description, Node);
	C.emitReport(std::move(Report));
	}
	};

	class BranchConditionCallbackTester final
	: public Checker<check::BranchCondition> {
	const BugType Bug{this, "BranchConditionCallbackTester"};

	public:
	void checkBranchCondition(const Stmt *Condition, CheckerContext &C) const {
	ExplodedNode *Node = C.generateNonFatalErrorNode(C.getState());
	if (!Node)
	return;
	const auto *FD =
	cast<FunctionDecl>(C.getLocationContext()->getStackFrame()->getDecl());

	std::string Buffer =
	(llvm::Twine("Within '") + FD->getIdentifier()->getName() +
	"': branch condition '")
	.str();
	llvm::raw_string_ostream OS(Buffer);
	Condition->printPretty(OS, /Helper=/nullptr,
	C.getASTContext().getPrintingPolicy());
	OS << "'";
	auto Report = std::make_unique<PathSensitiveBugReport>(Bug, Buffer, Node);
	C.emitReport(std::move(Report));

	C.addTransition();
	}
	};

	template <typename Checker> void registerChecker(CheckerManager &Mgr) {
	Mgr.registerChecker<Checker>();
	}

	bool shouldAlwaysRegister(const CheckerManager &) { return true; }

	void addBlockEntranceTester(AnalysisASTConsumer &AnalysisConsumer,
	AnalyzerOptions &AnOpts) {
	AnOpts.CheckersAndPackages.emplace_back("test.BlockEntranceTester", true);
	AnalysisConsumer.AddCheckerRegistrationFn([](CheckerRegistry &Registry) {
	Registry.addChecker(&registerChecker<BlockEntranceCallbackTester>,
	&shouldAlwaysRegister, "test.BlockEntranceTester",
	"EmptyDescription", "EmptyDocsUri",
	/IsHidden=/false);
	});
	}

	void addBranchConditionTester(AnalysisASTConsumer &AnalysisConsumer,
	AnalyzerOptions &AnOpts) {
	AnOpts.CheckersAndPackages.emplace_back("test.BranchConditionTester", true);
	AnalysisConsumer.AddCheckerRegistrationFn([](CheckerRegistry &Registry) {
	Registry.addChecker(&registerChecker<BranchConditionCallbackTester>,
	&shouldAlwaysRegister, "test.BranchConditionTester",
	"EmptyDescription", "EmptyDocsUri",
	/IsHidden=/false);
	});
	}

	llvm::SmallVector<StringRef> parseEachDiag(StringRef Diags) {
	llvm::SmallVector<StringRef> Fragments;
	llvm::SplitString(Diags, Fragments, "\n");
	// Drop the prefix like "test.BlockEntranceTester: " from each fragment.
	for (StringRef &Fragment : Fragments) {
	Fragment = Fragment.drop_until([](char Ch) { return Ch == ' '; });
	Fragment.consume_front(" ");
	}
	llvm::sort(Fragments);
	return Fragments;
	}

	template <AddCheckerFn Fn = addBlockEntranceTester, AddCheckerFn... Fns>
	bool runChecker(const std::string &Code, std::string &Diags) {
	std::string RawDiags;
	bool Res = runCheckerOnCode<Fn, Fns...>(Code, RawDiags,
	/OnlyEmitWarnings=/true);
	llvm::raw_string_ostream OS(Diags);
	llvm::interleave(parseEachDiag(RawDiags), OS, "\n");
	return Res;
	}

	[[maybe_unused]] void dumpCFGAndEgraph(AnalysisASTConsumer &AnalysisConsumer,
	AnalyzerOptions &AnOpts) {
	AnOpts.CheckersAndPackages.emplace_back("debug.DumpCFG", true);
	AnOpts.CheckersAndPackages.emplace_back("debug.ViewExplodedGraph", true);
	}

	/// Use this instead of \c runChecker to enable the debugging a test case.
	template <AddCheckerFn... Fns>
	[[maybe_unused]] bool debugChecker(const std::string &Code,
	std::string &Diags) {
	return runChecker<dumpCFGAndEgraph, Fns...>(Code, Diags);
	}

	std::string expected(SmallVector<StringRef> Diags) {
	llvm::sort(Diags);
	std::string Result;
	llvm::raw_string_ostream OS(Result);
	llvm::interleave(Diags, OS, "\n");
	return Result;
	}

	TEST(BlockEntranceTester, FromEntryToExit) {
	constexpr auto Code = R"cpp(
	void top() {
	// empty
	})cpp";

	std::string Diags;
	// Use "debugChecker" instead of "runChecker" for debugging.
	EXPECT_TRUE(runChecker(Code, Diags));
	EXPECT_EQ(expected({"Within 'top' B1 -> B0"}), Diags);
	}

	TEST(BlockEntranceTester, SingleOpaqueIfCondition) {
	constexpr auto Code = R"cpp(
	bool coin();
	int glob;
	void top() {
	if (coin()) {
	glob = 1;
	} else {
	glob = 2;
	}
	glob = 3;
	})cpp";

	std::string Diags;
	// Use "debugChecker" instead of "runChecker" for debugging.
	EXPECT_TRUE(runChecker(Code, Diags));
	EXPECT_EQ(expected({
	"Within 'top' B1 -> B0",
	"Within 'top' B2 -> B1",
	"Within 'top' B3 -> B1",
	"Within 'top' B4 -> B2",
	"Within 'top' B4 -> B3",
	"Within 'top' B5 -> B4",
	}),
	Diags);
	// entry true exit
	// B5 -------> B4 --> B2 --> B1 --> B0
	// \| ^
	// \| false \|
	// v \|
	// B3 -----------------------+
	}

	TEST(BlockEntranceTester, TrivialIfCondition) {
	constexpr auto Code = R"cpp(
	bool coin();
	int glob;
	void top() {
	int cond = true;
	if (cond) {
	glob = 1;
	} else {
	glob = 2;
	}
	glob = 3;
	})cpp";

	std::string Diags;
	// Use "debugChecker" instead of "runChecker" for debugging.
	EXPECT_TRUE(runChecker(Code, Diags));
	EXPECT_EQ(expected({
	"Within 'top' B1 -> B0",
	"Within 'top' B3 -> B1",
	"Within 'top' B4 -> B3",
	"Within 'top' B5 -> B4",
	}),
	Diags);
	// entry true exit
	// B5 ----------> B4 --> B3 --> B1 --> B0
	}

	TEST(BlockEntranceTester, AcrossFunctions) {
	constexpr auto Code = R"cpp(
	bool coin();
	int glob;
	void nested() { glob = 1; }
	void top() {
	glob = 0;
	nested();
	glob = 2;
	})cpp";

	std::string Diags;
	// Use "debugChecker" instead of "runChecker" for debugging.
	EXPECT_TRUE(runChecker(Code, Diags));
	EXPECT_EQ(
	expected({
	// Going from the "top" entry artificial node to the "top" body.
	// Ideally, we shouldn't observe this edge because it's artificial.
	"Within 'top' B2 -> B1",

	// We encounter the call to "nested()" in the "top" body, thus we have
	// a "CallEnter" node, but importantly, we also elide the transition
	// to the "entry" node of "nested()".
	// We only see the edge from the "nested()" entry to the "nested()"
	// body:
	"Within 'nested' B2 -> B1",

	// Once we return from "nested()", we transition to the "exit" node of
	// "nested()":
	"Within 'nested' B1 -> B0",

	// We will eventually return to the "top" body, thus we transition to
	// its "exit" node:
	"Within 'top' B1 -> B0",
	}),
	Diags);
	}

	TEST(BlockEntranceTester, ShortCircuitingLogicalOperator) {
	constexpr auto Code = R"cpp(
	bool coin();
	void top(int x) {
	int v = 0;
	if (coin() && (v = x)) {
	v = 2;
	}
	v = 3;
	})cpp";
	// coin(): false
	// +--------------------------------+
	// entry \| v exit
	// +----+ +----+ +----+ +----+ +----+ +----+
	// \| B5 \| --> \| B4 \| --> \| B3 \| --> \| B2 \| --> \| B1 \| --> \| B0 \|
	// +----+ +----+ +----+ +----+ +----+ +----+
	// \| ^
	// +---------------------+
	// (v = x): false

	std::string Diags;
	// Use "debugChecker" instead of "runChecker" for debugging.
	EXPECT_TRUE(runChecker(Code, Diags));
	EXPECT_EQ(expected({
	"Within 'top' B1 -> B0",
	"Within 'top' B2 -> B1",
	"Within 'top' B3 -> B1",
	"Within 'top' B3 -> B2",
	"Within 'top' B4 -> B1",
	"Within 'top' B4 -> B3",
	"Within 'top' B5 -> B4",
	}),
	Diags);
	}

	TEST(BlockEntranceTester, Switch) {
	constexpr auto Code = R"cpp(
	bool coin();
	int top(int x) {
	int v = 0;
	switch (x) {
	case 1: v = 10; break;
	case 2: v = 20; break;
	default: v = 30; break;
	}
	return v;
	})cpp";
	// +----+
	// \| B5 \| -------------------------+
	// +----+ \|
	// ^ [case 1] \|
	// entry \| v exit
	// +----+ +----+ [default] +----+ +----+ +----+
	// \| B6 \| --> \| B2 \| ----------> \| B3 \| --> \| B1 \| --> \| B0 \|
	// +----+ +----+ +----+ +----+ +----+
	// \| ^
	// v [case 2] \|
	// +----+ \|
	// \| B4 \| -------------------------+
	// +----+

	std::string Diags;
	// Use "debugChecker" instead of "runChecker" for debugging.
	EXPECT_TRUE(runChecker(Code, Diags));
	EXPECT_EQ(expected({
	"Within 'top' B1 -> B0",
	"Within 'top' B2 -> B3",
	"Within 'top' B2 -> B4",
	"Within 'top' B2 -> B5",
	"Within 'top' B3 -> B1",
	"Within 'top' B4 -> B1",
	"Within 'top' B5 -> B1",
	"Within 'top' B6 -> B2",
	}),
	Diags);
	}

	TEST(BlockEntranceTester, BlockEntranceVSBranchCondition) {
	constexpr auto Code = R"cpp(
	bool coin();
	int top(int x) {
	int v = 0;
	switch (x) {
	default: v = 30; break;
	}
	if (x == 6) {
	v = 40;
	}
	return v;
	})cpp";
	std::string Diags;
	// Use "debugChecker" instead of "runChecker" for debugging.
	EXPECT_TRUE((runChecker<addBlockEntranceTester, addBranchConditionTester>(
	Code, Diags)));
	EXPECT_EQ(expected({
	"Within 'top' B1 -> B0",
	"Within 'top' B2 -> B1",
	"Within 'top' B3 -> B1",
	"Within 'top' B3 -> B2",
	"Within 'top' B4 -> B5",
	"Within 'top' B5 -> B3",
	"Within 'top' B6 -> B4",
	"Within 'top': branch condition 'x == 6'",
	}),
	Diags);
	}

	} // namespace